It's quite funny really. I was playing DN3D Atomic Edition before I was old enough to legally buy it (the PC version was an 18 back then). And that was roughly when they announced DNF. Now I'm 27. Scary thought.
I've said it already though - it's a Duke Nukem game. It doesn't need to be the best looking game around, it doesn't need to be all that original in the storyline department, it just needs to keep up the humour and being a complete parody of itself that DN3D was. It's about shooting aliens because you can, not because of some deeper reason. If they can avoid just porting the same jokes and comments from DN3D and keep up the standard, it'll be worth the wait. Nearly.
3D Realms are saying there's a gameplay movie coming soon, so that'll really be the one to watch for. Rendered sequences are all well and good, but they don't tell you much. And quite what their definition of "soon" is now, is anyone's guess.